1. Technical Field
The present invention relates to the technical field pertaining to substrates for electrooptic devices such as organic electro-luminescence (EL) devices or liquid crystal devices, electrooptic devices including such substrates, methods for making the electrooptic devices, and electronic apparatuses including the electrooptic devices.
2. Related Art
Electrooptic devices of this type display images by controlling switching of pixel electrodes by using pixel switching elements in the individual pixel sections through an active matrix driving technology, for example.
On a substrate, a pixel electrode is formed in a layer different from that of a pixel switching element, and a conductive layer, a relay layer, or a relay electrode is formed to provide electrical connection between the pixel electrode and the pixel switching element. Then, an organic resin film that can form a surface with satisfactory flatness is formed to provide interlayer insulation between the pixel electrode and the pixel switching element and the pixel electrode and the conductive layer. The surface of the pixel electrode maintains satisfactory flatness since the pixel electrode is formed above the organic resin film.
JP-A-10-39334 and JP-A4-163528 each disclose a technology for forming an inorganic insulating film composed of, for example, a nitrogen-containing material above the organic resin film and below the pixel electrode such that, during the manufacture or operation of electrooptic devices, film separation and cracking of the pixel electrode due to swelling of the water-absorbent organic resin film can be prevented.
In particular, according to JP-A-10-39334 and JP-A-4-163528, a small hole is formed in an organic resin film to expose the surface of a conductive layer, and an inorganic insulating film is continuously formed from inside the small hole to outside the small hole such that sidewall of the small hole is covered with the film. In this case, the inorganic insulating film on the sidewall inside the small hole forms a contact hole, and the pixel electrode electrically connects to the conductive layer through this contact hole without making contact with the organic resin film.
Another inorganic insulating film composed of, for example, a nitrogen-containing material is formed above the pixel switching elements and the conductive layers but below the organic resin film to protect the switching element. In a plan view, this another inorganic insulating film is patterned prior to formation of the organic resin film such that the surface of a portion of the conductive layer to be electrically connected to the pixel electrode is exposed from the another inorganic insulating film in the region where the another inorganic insulating film overlaps the conductive layer.
JP-A-2003-308027 discloses a structure in which a pixel electrode is electrically directly connected to a pixel switching element through a contact hole formed in a small hole in the organic resin film.
In pages 1017 to 1019 of Society for Information Display 2004 Digest (2004), a so-called micro cavity structure used in an organic EL device that uses an organic EL as an electrooptic material is disclosed as an example of the electrooptic device. According to this micro cavity structure, the organic EL is composed of a material that can emit light corresponding to white, and in the pixel unit, a reflector film is disposed below the pixel electrode. Moreover, color layers for red, green, and blue are formed on the substrate so that each color layer in the corresponding pixel unit faces the pixel electrode with the organic EL therebetween.
However, according to the technology disclosed in JP-A-10-39334 and JP-A-4-163528, the organic resin film comes into contact with the surface of the conductive layer exposed in the another inorganic resin film disposed below the organic resin film. Thus, after forming the small hole, an organic substance derived from the organic resin film may remain on the surface of the conductive layer, and this increases the resistance related to the electrical connection between the pixel electrode and the conductive layer, i.e., the contact resistance, and makes the contact resistance non-uniform among contact holes, thereby disadvantageously degrading the contact properties.
According to the technology disclosed in JP-A-2003-308027, a signal line or an electrode electrically connected to a pixel switching element lies in the same layer as the pixel electrode, resulting in a decreased aperture ratio. In order to overcome this problem, cumbersome procedures such as modifying design of wiring that constitutes the pixel unit are necessary, and the cost required for the production of the electrooptic device may thus increase.
Moreover, according to the micro cavity structure disclosed in pages 1017 to 1019 of Society for Information Display 2004 Digest, the reflector film comes into direct contact with the pixel electrode. Thus, it becomes necessary to prevent separation of the reflector film resulting from pinholes in or deposited dust on the surface of the reflector film during formation of the pixel electrode.